The present invention relates generally to tape reproducing system, and more specifically to a method and an apparatus for detecting inter-program pauses between successively recorded programs. The invention also relates to a tape reproducing system in which a desired recorded program is automatically detected and reproduced in response to a manual instruction.
Operating a tape recorder in search of a desired material from among successively recorded programs is tedious. Automatic detection of a program is desired to eliminate this problem. To permit automatic program searching the tape is driven in the fast-forward or rewind mode in slight contact with a playback transducer head for high-speed reproduction of the recorded material so a sensing circuit can detect inter-program pauses. Since the tape is driven at a constant speed by a capstan-pinch roller arrangement during playback, the successively recorded materials are spaced an equal distance apart throughout the length of the tape. However, during the fast-forward or rewind mode the tape is driven at a high speed by takeup reel or supply reel, respectively, to which the rotary torque of a motor is coupled by means of a known slip-friction mechanism. However, because of the higher speed of rewind and fast forward operations the motor tends to be overloaded as a function of the amount of tape wound on that reel. As a result, the rotational speed of each reel varies nonlinearly as a function of the diameter of the tape wound on the power-coupled reel.
Therefore, the detected interval of the inter-program pause portions varies significantly from point to point along the length of the tape. On the other hand, the signal level of each recorded program varies significantly so that in certain instances it is reduced to a minimum level. If such low level signals persist for a substantial period of time, they are likely to be detected as inter-program pauses.
U.S. Pat. No. 4,288,823 discloses an apparatus for and method of distinguishing pauses to control replay in a type reproduction system wherein a speed sensor generates a tape speed signal which is coupled to a first counter and converted into a corresponding tape speed digital value. A pause detector detects programs and pauses to derive the duration of each detected pause. A second counter converts an output of the pause detector into a corresponding pause-duration digital value. The tape speed and pause-duration digital values are compared against each other to generate a control signal for replaying the recorded programs. However, the nonlinear relationship between the tape and reel speeds is not taken into account. Thus, the comparison does not serve as an accurate indication of inter-program pauses.